In order to optimize the supply of power to an electronic circuit (in particular in the case of digital circuits), it has been proposed to adapt the supply of power to the performance required at a given time in the operation of the electronic circuit.
The current design of numerous electronic circuits, in particular digital electronic circuits (and notably those produced in CMOS technology), is such that the energy consumed to perform a given set of operations increases with the power supply voltage used, which is imposed by the frequency at which the circuit is required to operate.
It has thus appeared possible to optimize power consumption by adapting the supply voltage to a level as low as possible but sufficient to ensure reliable operation at the required level of performance (i.e. at the required clock frequency in the case of a synchronous circuit).
The paper “Low-Power Operation Using Self-Timed Circuits and Adaptive Scaling of the Supply Voltage” by L. S. Nielsen et al. in the journal IEEE VLSI volume 2, number 4, December 1994, thus introduces the concept of adaptive voltage scaling in the context of asynchronous logic systems.
Adapting the supply voltage to the operating frequency of synchronous digital circuits has also been proposed, notably in the papers “A Dynamic Voltage Scaled Microprocessor System”, by T. D. Burd et al., in the journal IEEE JSSC volume 35, number 11, November 2000, and “Closed-Loop Adaptive Voltage Scaling Controller for Standard-Cell ASICs”, by S. Dhar et al., in proceedings of ISLPED, August 2002.
Other solutions have been proposed more recently in the same line of thinking, notably in the paper “Dynamic Voltage and Frequency Management for a Low-Power Embedded Microprocessor”, by M. Nakai et al., in the journal IEEE JSSC volume 40, number 1, January 2005, and in the paper “Next Generation SoC Power Management”, by J. Pennanen et al., in the journal Electronics Product Design, March 2007.
Although these systems make it possible to optimize electrical power consumption by adapting the supply voltage to the performance constraints of the electronic circuit (generally expressed in terms of the operating frequency required by the applications implemented by the electronic circuit), on the other hand, because of their design, they require a power supply module able to deliver a voltage variable over a continuous range of values throughout operation, generally implemented in the form of a DC-DC converter.
The presence of such a module causes problems regardless of the technology envisaged: the use of external choppers is naturally not suited to the integration of all the components in an integrated circuit; because of the presence of numerous passive components, the use of internal choppers is very costly (in terms of substrate area or because of the processes used); as for linear converters, they suffer from low efficiency.